A Power-over-Ethernet (PoE) system includes Power Source Equipment (PSE) to provide a PoE voltage over an Ethernet cable to a Powered Device (PD) to power the PD. Conventionally, the PSE supplies the PoE voltage within a limited PoE voltage range, such as 44-57 Volts (V) as defined in the IEEE 802.3 standard. The supplied PoE voltage is generally set to be substantially higher than a voltage actually needed to power circuits in the PD so as to reduce a power transmission loss in the Ethernet cable connecting the PSE to the PD. The PD typically includes a Direct Current-to-Direct Current (DC-DC) voltage converter to convert the higher voltage down to a lower voltage useable by the circuits in the PD, such as 5V or 12V. The DC-DC voltage down-conversion incurs a DC-DC power efficiency conversion loss in the PD.